December 2010: Do You Have a 6 Bit LCD Monitor?
In need of a new LCD monitor recently, I went searching at the
local Best Buy for a suitable replacement. Even though I gave up on
trying to get my recently acquired Mac computer to do anything useful and I
eventually returned it, that Apple Cinema display was just gorgeous! In
fact, it spoiled me to the point that looking at my existing LCD PC monitor
made me almost wish I had that Mac back on my desk. So I went in
search of a good LCD monitor for my Windows 7 system. Surely I thought,
technology has improved in the past ~3 years since I bought my last LCD
monitor and I'd be able to just run to the local store and buy one equivalent
to the Apple Cinema displays? What I found were a host of new-tech LED
backlit LCD displays that looked like they had potential by their specs, but
after going to the store to review them, I was in for a big surprise. I
ended up losing almost 2 days of work trying to sort out the junk that is
being sold now, researching different panel types such as TN versus IPS
panels, and somewhere along the way, picking up on what appears to be a well
guarded secret in the industry: that your typical LCD monitor that you find at
your local brick and mortar stores can only display about 262,000 colors and
not the 16.7 million that is being used by your 24 or 32 bit video board!
Read on if you want the details...
LED Backlit Monitors
The latest craze in LCD monitors are those that
have LED backlighting. Like the new LED TV's, they are basically the
same LCD technology but their backlight uses LEDs instead of a fluorescent
light source. The advantage is lower cost, lower power consumption, and
potentially smoother (more even) lighting across the screen. What I
found with the latest crop of LED monitors, however, is that because they are
so light and thin (due to the LED lighting), the manufacturers seem to be
using stands that are, simply put, a joke! Even the high end models
costing $300 from well known and respected brands use nothing more than a
cheap plastic base that basically wobbles if you breathe on it! In
addition, instead of finding that the LED backlighting improved color like I
expected, I found just the opposite. I found the LED backlighting to be
harsh and it caused strange color shifts that are unacceptable for
Whites have that harsh bluish glow (reminiscent
of an LED flashlight) that make white shirts and other bright details look a
bit pasty. I tried two high end monitors from two different brands and
have the same judgment about both of them: not suitable for photographic work.
Unlike LED TV's that seem to have better viewing angles, I found the viewing
angles on the LED backlit LCD monitors to be almost as bad as old-tech LCD
monitors. The top of the monitor looks darker than the bottom and any
shift of your head in front of the monitor causes color and contrast changes.
Knowing that it can be done right (the Apple Cinema displays don't have those
problems), I ended up returning two of the LED LCD monitors and digging in to
do a little deeper research.
TN LCD Panels
The first thing I found when researching why
some monitors have such a contrast/angle issue is that almost all of your
"standard" LCD monitors that you find in brick and mortar stores (including
the LED backlit ones) use a panel technology called TN, short for Twisted
Nematic. While TN panels are cheaper and lighter than other
technologies, they all suffer from the same contrast issues at different
angles. The TN technology is the reason that, if you fill your entire
LCD monitor with a single shade of gray, the top of the monitor will look
significantly darker than the bottom on a TN based panel. The story only
gets worse from there!
What I found next is that in general, TN LCD panels can only
display 6 bits per color channel. Your images, your video card, and your
display properties say you are running "True Color (32 bit)", yet you are only
getting 18 bits of color that amounts to 262,000 colors, not the 16.7 million
you thought you were getting! Suddenly things started to make sense.
I've noticed for years that, when I display a gray gradient when doing
graphics work (0,0,0 through 255,255,255), I could see clear and obvious
banding in the grays. It was noticeable: much more noticeable than it
should be if I truly had 256 shades (8 bits) of gray. I always blamed it
on my monitor colorimeter that I use to profile my monitor, but now it made
sense. These "run of the mill" LCD displays that I've been using for
years can only display 64 shades of any given color, not 256. They try
to hide that fact (some better than others) by dithering or high frequency
color shifting, but it will be noticeable to most people.
I started to wonder how many people realize that, if they went
into some local electronics store like Best Buy, Staples, Office Depot, etc.
and walked out with an LCD monitor, chances are they just bought a monitor
that can only display 262,000 colors. Is this a "big secret" of the
industry? I wondered why, on this latest crop of LCD monitors, they
offer a "sharpness" setting. Why would such a thing even be necessary on
a monitor where each pixel should be driven individually with sharpness being
an attribute of the display software? Why, when you crank up the
sharpness, does text get color halos around it and when you turn it down, it
gets blurry, and there seems to be no in between? It all started to come
together now. Text is antialiased which means it isn't just black or
white. There are shades of gray... shades of gray that these LCD
monitors based on the cheap TN technology can't display so it dithers the
edges! It just isn't true color (24 or 32 bit) and it affects everything
from text to photos. I wonder, like me, how many people fiddle with the
sharpness on their LCD monitor only to find that one value (say 4) makes your
text look blurry yet moving it to the next value (say 5) makes halos/artifacts
appear around the text which makes it less readable? That's the TN panel
at work, trying to make the most of a limited color scheme!
IPS LCD Panels
I was finally able to find that the Apple
Cinema displays are based on a better LCD technology called IPS, short for
In-Plane Switching. The details of the technology aren't as important
as what it does for us consumers, particularly those of us who are into
photography! IPS panels are considered "professional grade" and they
not only offer the full 16.7 million colors that 24 bit color (8 bits x 3
channels) provides, but they also offer smooth color response with almost no
color shift based on viewing angle. In addition, while the cheaper TN
panels have a small color range (typically about 75% to 80% of the NTSC
color space at best), the IPS panels can display more (and more vibrant)
colors and typically cover a color space even larger than NTSC (about 110%
or higher of NTSC color space).
it is possible to spend $1000 or more on such LCD panels, I did manage to
find several that were the same price or even cheaper than the $299 TN
panels being sold at local stores! The one I ended up with was a
Viewsonic VP2365wb that I got for $269 but there are HP ZR series monitors
in that price range as well, and a few other brands that get good reviews.
As soon as I connected the VP2365wb, I immediately realized what I had been
missing. Gradients were smooth again, text was razor sharp, and the
color is simply magnificent. I thought to myself, "I can definitely
live with this monitor"! This monitor was in the same league as the
Apple Cinema Displays. I felt like I had cracked the big secret of the
el-cheapo monitors yet somehow I felt misled about what I had been buying
previously. Buyer beware! I would recommend checking the panel
technology of any monitor before you buy. Of course, the manufacturers
seem satisfied with keeping that a secret as well, since you'll rarely find
the "panel technology" in specs. What you can do is search the model
number and "TN" to see if anyone is talking about that model on (for
example) forums: they may mention that your model is a TN or IPS model.
My recommendation, at least for photography: stay away from TN based LCD
S-IPS, H-IPS, MVA, PVA, and Other Confusing
There are a lot of
acronyms out there for different LCD display technologies but the most popular
panel type for a good LCD display seems to be IPS at the current time.
Whether S-IPS, H-IPS, or some other incarnation, the "IPS" part is what is
important. I managed to find a decent list of IPS monitors and this is
where I started my research. If you are interested, you can
check it out
Here are some of the
highlights of what you'll get if you buy an IPS monitor (versus the typical TN
type LCD's sold in most stores):
Much better (more consistent) viewing at angles
Almost no contrast, color, or brightness shift from top to bottom of monitor
Much greater color range (gamut)
Smoother color with less banding: can display entire 16.7 million color range
And the only con I could find:
I'm a software engineer by
nature and I don't typically have time to follow all the latest trends in
hardware, so maybe I'm a bit behind in "monitor tech" but I bet there are a lot
of LCD monitor buyers out there who don't realize that their monitor can only
display 6 bits (64 shades) of color per color channel, or about 262,000 colors.
The LCD monitors sold in almost all brick and mortar stores are based on TN
panels which basically amount to old/cheap technology. Even the newest LED
backlit LCD monitors fall into this category of monitors that still have large
contrast differences based on viewing angle and a limit of 262,000 colors.
This seemed like a "dark secret of the industry" that wasn't well known, so I
wrote this article to help out. If you've ever seen noticeable banding in
gradients (like gray gradients) on your monitor, noticed that text isn't as
sharp as it should be or text that has halos around it, or you notice that the
image on your monitor gets very dark when you move your head down a bit, you've
probably got a TN panel with these limited characteristics. To be sure,
you can do a web search and enter the model number of your monitor and the
letters TN to see if you get hits telling you that your monitor is a TN panel.
If so, you're likely not getting the best image for photography. You'll
have to be the judge if whether or not this matters to you. For me, I
guess ignorance was bliss... until I saw what I was missing.
There is hope. Get
an IPS panel to solve all of the above problems!
will take you to a list where you can find professional grade IPS based LCD
monitors and some are no more expensive than what you'll pay for the LCD
monitors based on cheap TN technology that you'll see in a brick and mortar
store! While I've noticed clear banding artifacts when displaying (for
example) a gray gradient on the non-IPS monitors, I rarely hear anyone complain
that their monitor is only 6 bits per channel and can only display 262,000 of
the 16.7 million colors provided by their graphics card. Kinda makes me
wonder, if you don't see that or at least you don't notice it, how can you
possibly see the difference between a 24 bit (8 bit/channel) and a 48 bit (16
bits/channel) print? Most people, even those who never realized that their
existing LCD monitor could only display 6 bit color depth, still use their
monitor as the benchmark and they try to match their prints to the monitor.
Their monitor is 6 bits yet they bought a printer that advertised it could print
16 bits just because, well, 16 sounded better than 8. And there you have
the full spectrum of how manufacturers sell products to consumers: from
overrating (selling something that can't quite do what you assume it can) to
overhyping (selling numbers you can't see or realize) at the other, and
everything in between. Food for thought!
Mike Chaney, author,
Qimage, Profile Prism, FlashPipe, TT Dyno
« Last Edit: November 10, 2010, 12:51:33 PM by Mike Chaney »